In the case of catamenial pads, women have come to expect a high level of performance in terms of comfort and fit, retention of fluid, and minimal staining. Above all, leakage of fluid from the pad onto undergarments is regarded as totally unacceptable. Improving the performance of such catamenial pads continues to be a formidable undertaking, although a number of improvements have been made in both catamenial structures, and materials used in such structures. However, eliminating leakage, particularly along the inside of the thighs, without compromising fit and comfort, has not always met the desired needs of the consumer.
Leakage from catamenial pads, and in particular sanitary napkins, is generally attributed to a high concentration of fluid at the point where the menses exits the body and immediately contacts the surface of the napkin. At this point of deposit, the napkin absorbent structure can become quickly supersaturated. The blood migrates radially from this point and leaks from the sides nearest the wearer's legs.
This leakage problem for catamenial pads generally, and sanitary napkins in particular, is especially acute for thinner versions of such products. Thinness is a highly desired characteristic in such products. For example, thinner sanitary napkin products are less bulky to wear, fit better under clothing and are less noticeable. Thinner sanitary napkins are also more compact in the package, making them easier to carry and store.
The users of sanitary napkins, and the like, have also come to expect the surface of such products to provide a cleaner, more sanitary and drier aspect than common cloth or nonwoven materials have historically provided. Current sanitary napkin products are typically provided with nonwoven or formed-film permeable topsheets that are designed to move discharged menstrual fluids rapidly therethrough and into an underlying absorbent structure. This rapid movement of acquired menstrual fluids is designed to provide a drier and cleaner surface adjacent the wearer of the product.
The absorbent structures of current catamenial (e.g., sanitary napkin) pads have typically comprised one or more fibrous layers for acquiring the discharged menstrual fluid from the permeable topsheet and distributing it to an underlying storage area. Absorbent structures for relatively thin versions of prior catamenial products usually comprise a fluid acquisition layer (often called a "secondary topsheet") that is adjacent to the permeable topsheet This "secondary topsheet" typically is made from an air-laid-tissue web or a synthetic nonwoven. Underlying this secondary topsheet is the main absorbent core that is typically made from air-laid or wet-laid tissue. The absorbent core often contains a particulate absorbent gelling material that can be encased or enveloped within this tissue. Such encased or enveloped cores are often referred to as tissue laminate cores. See, for example, U.S. Pat. No. 4,950,264 (Osborn), issued Aug. 21, 1990 and U.S. Pat. No. 5,009,653 (Osborn), issued Apr. 23, 1991, that disclose tissue laminate cores used in sanitary napkin products.
The "secondary topsheet" in these prior catamenial absorbent structures is supposed to rapidly draw discharged menstrual fluid through the permeable topsheet so that the surface adjacent the wearer of the article remains relatively clean and dry. The menstrual fluid acquired by the "secondary topsheet" is then distributed to the underlying absorbent core for distribution to the absorbent gelling material for ultimate storage. Unfortunately, the "secondary topsheet" in these prior catamenial absorbent structures tends to collapse when wetted and compressed during use. The fibrous portion of the underlying absorbent core also tends to be dimensionally unstable when wetted (i.e., can either expand or collapse), thus changing its density and pore size distribution. This makes it more difficult to rapidly and adequately transfer menstrual fluid to the absorbent gelling material for storage, especially in "gush" situations. When wetted, the fibrous portion of the absorbent core also become less stiff (due to the elimination of hydrogen bonding between the fibers). Collapse and consolidation of the fibrous portion of the core also results in the product bunching during use.
As a result of these changes that occur during use, prior catamenial absorbent structures have a number of problems. One is the difficulty in insuring adequate topsheet dryness. In particular, the acquired menstrual fluid can potentially leak back through the main topsheet. This phenomenon is often referred to as "rewet." This potential for "rewet" increases as the absorbent structure becomes super saturated with acquired menstrual fluid.
Another problem of prior catamenial absorbent structures is a lower total fluid capacity. Basically, this means only so much of the absorbent gelling material in the absorbent core is effectively utilized to absorb menstrual fluid. The remaining absorbent gelling material a is either underutilized or is not utilized at all. Under utilization is a particular problem for absorbent cores, such as tissue laminates, having high concentration of absorbent gelling material.
These prior catamenial absorbent structures, and in particular catamenial pads using such structures, have had a greater chance of causing panty and body soiling. This is because the absorbent structure lacks resilience, leading to bunching of the pad. This lack of resilience, and consequent bunching, has also caused these prior catamenial pads to provide poorer fit and comfort for the user.
Accordingly, it would be desirable to provide catamenial absorbent structures, as well as catamenial pads embodying such structures that: (1) improve topsheet dryness, even in "gush" situations; (2) have an increased total fluid capacity and ability to retain absorbed fluids so as to reduce "rewet"; (3) have reduced panty and body soiling; and (4) provide improved fit and comfort for the user.